At around 4 p.m. on Sunday, a group of Vietnamese coast guard and fisheries surveillance vessels anchored 12 nautical miles from the Haiyan Shiyou-981 rig spotted a phalanx of five Chinese vessels approaching from the direction of the rig.

A Chinese tugboat coded 32 led the line and approached a Vietnamese fisheries surveillance ship, which switched on loudspeakers and demanded that the Chinese vessels leave the area.